For their power supply, active medical implants either have an energy storage mechanism (battery, capacitor) or are constantly supplied with power transcutaneously (via cable, HF, alternating magnetic field). A transcutaneous power supply can be used for only short periods of time because there is a high risk of infection or the constant HF burden can lead to tissue damage. Therefore, this has not been successful in medical practice on a large scale.
Energy storage mechanisms become depleted after a certain amount of time and must be replaced or recharged. Replacing the energy storage mechanism is necessarily associated with explantation of the entire device and reimplantation of the same device and/or a replacement device. In the past, this was the most common procedure, but it is complicated, expensive and associated with medical risks and considerable discomfort for the user of the implant.
An extracorporeal primary coil and a secondary coil inside the implant are generally used to charge a rechargeable energy storage mechanism (battery) of an active implant. Power is transmitted from the primary coil to the secondary coil through an alternating magnetic field. The maximum transmissible energy is limited by heating of the tissue in the passage of energy. A charging cycle of the energy storage mechanism may also become very long due to the low energy transfer rate. Conventional rechargeable chemical cells have a longer lifetime if they are charged regularly and frequently and thus always have a high level of charge. Depending on the use of the transcutaneous energy transfer, the rechargeable cell may become very highly discharged before the charging operation, thus reducing the lifetime of the cell. Maintaining regular charging cycles to maintain the function of the implant is the responsibility of the physician or the patient. In the physician's practice, it requires a great deal of organizational effort and discipline on the part of the patient but this is often not adequately ensured in practice.
The present invention is directed toward overcoming one or more of the above-identified problems.